| 摘要 |
An apparatus and method to significantly improve performance of certain group queries using an encoded vector index (EVI) is disclosed. An EVI provides the data necessary to generate query results for COUNT, SUM, MIN, and MAX commands that specify the one or more database fields upon which the EVI is built. Only the EVI symbol table's key count, and the one or more database fields duplicated in the EVI symbol table are necessary to generate the query results. The key count in each EVI symbol table entry contains the number of records in the database having identical values in the EVI fields (that is, the fields upon which the EVI is built). These duplicated database values are called key values in the EVI symbol table entry. The EVI symbol table entry's key count allows quick generation of query results for COUNT and SUM commands that specify one or more EVI fields. SUM command processing of an EVI field is further facilitated by calculating a product of the key count and the key value of that EVI field. The highest or lowest key value in an EVI field provides query results for MAX or MIN commands specifying that EVI field. A HAVING operand specifying a key value delimiter on an EVI field for any of the aforementioned grouping commands is also facilitated using the EVI symbol table.
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